Apparatus for extracorporeal treatment of blood and method of priming an extracorporeal blood circuit

ABSTRACT

An extracorporeal blood treatment apparatus comprises: a blood treatment device ( 2 ); an extracorporeal blood circuit comprising a blood withdrawal line ( 6 ) and a blood return line ( 7 ) coupled to the extracorporeal blood treatment device ( 2 ), wherein the blood return line ( 7 ) presents a heating zone ( 14 ) coupled or configured to be coupled to a blood warmer ( 15 ); a blood pump ( 6 ) configured to be coupled to a pump section of the blood withdrawal line ( 6 ); at least a post-infusion line ( 13, 13 ′) connected to the blood return line ( 7 ) upstream of the heating zone ( 14 ); an air trapping device ( 9 ) placed on the blood return line ( 7 ) upstream of the heating zone ( 14 ).

PRIORITY CLAIM

The present application is a National Phase of International ApplicationNo. PCT/EP2018/068063, filed Jul. 4, 2018, which claims priority to EPApplication No. 17182162.2, filed Jul. 19, 2017, the entire contents ofeach of which are incorporated herein by reference and relied upon.

FIELD OF THE INVENTION

The present invention relates to an apparatus for extracorporealtreatment of blood. The extracorporeal treatment apparatus according tothe invention is combined with, or comprises, a blood-warming device.The invention also concerns a method of priming an extracorporeal bloodcircuit, before starting patient treatment, wherein the blood-warmingdevice may be part of the extracorporeal blood treatment apparatus ormay be a separate device which is in communication with theextracorporeal blood treatment apparatus.

Extracorporeal blood treatment involves removing blood from a patient,treating the blood externally to the patient, and returning the treatedblood to the patient. Extracorporeal blood treatment is typically usedto extract undesirable matter or molecules from the patient's bloodand/or add desirable matter or molecules to the blood. Extracorporealblood treatment is used with patients unable to effectively removematter from their blood, such as when a patient has suffered temporaryor permanent kidney failure. These patients and other patients mayundergo extracorporeal blood treatment to add or remove matter to theirblood, to maintain an acid/base balance or to remove excess body fluids,for example.

Extracorporeal blood treatment is typically accomplished by removing theblood from the patient in e.g. a continuous flow, introducing the bloodinto a primary chamber, also referred to as blood chamber, of atreatment unit (such as a dialyzer or an hemofilter) where the blood isallowed to flow past a semipermeable membrane. The semipermeablemembrane selectively allows matter in the blood to cross the membranefrom the primary chamber into a secondary chamber and also selectivelyallows matter in the secondary chamber to cross the membrane into theblood in the primary chamber, depending on the type of treatment.

A number of different types of extracorporeal blood treatments may beperformed. In an ultrafiltration (UF) treatment, undesirable fluid isremoved from the blood by convection across the membrane into thesecondary chamber. In a hemofiltration (HF) treatment, the blood flowspast the semipermeable membrane as in UF (where waste and undesirablefluid are removed) and desirable matter is added to the blood, typicallyby dispensing a fluid into the blood either before and/or after itpasses through the treatment unit and before it is returned to thepatient. In a hemodialysis (HD) treatment, a secondary fluid containingdesirable matter is introduced into the secondary chamber of thetreatment unit. Undesirable matter from the blood crosses thesemipermeable membrane into the secondary fluid by diffusion anddesirable matter from the secondary fluid crosses the membrane into theblood. In a hemodiafiltration (HDF) treatment, blood and secondary fluidexchange matter as in HD, and, in addition, matter is added to theblood, typically by dispensing a fluid into the treated blood (infusion)either before and/or after it passes through the treatment unit andbefore its return to the patient as in HF.

During extracorporeal blood treatment therapies, the patient may loosesignificant amount of heat due to infusion fluids having lowertemperature than blood, due to fluid exchange across the membrane of thetreatment unit, and due to heat lost to the atmosphere. Asextracorporeal blood treatments may last from several hours up toseveral days, the patient is put at risk of hypothermia in case nopreventive measures are taken. This risk is, for example, present bothin the case of relatively short treatments with high volume exchange,like chronic HD or HDF, and in the case of low volume but continuoustherapies like continuous renal replacement therapy (CRRT) (used in e.g.acute HD). Furthermore, the risk of hypothermia is even more problematicin case of treatments applied to low body weight patients, such aschildren. Blood cooling due to fluid exchange (treatment and/or infusionfluids) is usually more important than heat losses to atmosphere in thecomplete extracorporeal blood circuit. In order to prevent hypothermiaduring extracorporeal blood treatment several solutions have beendeveloped in the past.

BACKGROUND

In accordance with a known solution, and in order to solve the aboveproblems, blood warmers acting on the bloodline and capable of directlywarming blood have been used. Blood warming brings the benefit ofoperating the filter device (in hemodialysis—HD—,hemodiafiltration—HDF—or hemofiltration in pre-dilution—HFpre—therapies)at a cooler temperature with respect to warming the therapy fluids,since using room temperature fluids. Cooler blood temperature in thefilter device is expected to decrease intensity of blood-materialsinteractions, thus improving biocompatibility and reducing clottingrisks.

Document WO 00/41746 discloses an integrated CRRT method and apparatuswhich incorporates steps and devices for compensating for heat loss fromblood in an extracorporeal circuit. A blood warmer is designed to engageand hold a disposable blood tube segment to transfer heat at a closelycontrolled temperature to blood flowing in the disposable blood tubesegment. The blood tube segment for engagement with the blood warmer islocated in downstream of a dialyzer and upstream of a venous pressuremonitor, an air bubble detector and a venous line clamp. The disposableblood tube segment may be selectively connected when heat losscompensation is required and left disconnected when heat losscompensation is not required.

Document U.S. Pat. No. 6,336,910 B1 discloses an extracorporealcirculation apparatus used when conducting a cooling method employed invarious medical treatments in humans. A diluent from a diluent containeris cooled in a heat exchanger and injected into the body. Blood iswithdrawn from the catheter, it passes through a blood concentrationdevice, it is heated to a temperature near 37° C. in the heat exchangerand then it is injected back into the body via a catheter. Theconcentration of the blood means the increase in or the recovery of thehematocrit value of the diluted blood drawn out from a body may beperformed by means of a filtration or dialysis treatment. Such atreatment may be performed by using an ordinary hemofilter which is usedin an artificial kidney apparatus. A drip chamber for removing bubblesmay be provided between the concentration element and the heatexchanger.

A disadvantage of the cited prior art documents may concern the safetyof the extracorporeal blood treatment apparatuses provided withblood-warming devices for heat compensation. Indeed, air bubblescontained in blood flowing through the blood-warming device (airtrapping in the blood-warming device) may lead to development of ‘hotspots’ and heating problems in the blood-warming device and/or may leadto early clotting of the blood circuit. Such events may lead to bloodloss and put patient safety at risk if recurring over time.

In addition, this fact may generate significant constraints in theblood-warming device design and may cause an increase of their designand production costs, since said blood-warming devices shall be designednot to trap any bubbles.

In particular, these problems are crucial for those apparatuses forextracorporeal treatment of blood provided with high infusion rates andlarge number of infusion lines, since blood is cooled a lot and theblood-warming device shall provide a large amount of heat to the bloodto restore the correct temperature.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention toimprove the safety of extracorporeal blood treatment apparatuses coupledto a blood-warming device (wherein the blood-warming device may be partof the extracorporeal blood treatment apparatus or may be a separatedevice, which is in communication with the extracorporeal bloodtreatment apparatus).

It is a further object of the present invention to provide an apparatusfor extracorporeal treatment of blood which allows to reduce or preventair trapping in the blood-warming device. It is a further object of thepresent invention to provide an apparatus for extracorporeal treatmentof blood which allows to protect the blood-warming device from therepeated presence of air bubbles at its flow inlet.

At least one of the above objects is substantially achieved by providingan air trapping device at the inlet of the blood warming device placedon the blood return line of the apparatus for extracorporeal treatmentof blood.

Aspects of the invention are disclosed in the following.

In accordance with a 1^(st) independent aspect, an extracorporeal bloodtreatment apparatus comprises:

a blood treatment device;

an extracorporeal blood circuit comprising a blood withdrawal line and ablood return line coupled to the blood treatment device, wherein theblood return line presents a heating zone coupled or configured to becoupled to a blood warmer;

a blood pump configured to be coupled to a pump section of theextracorporeal blood circuit, e.g. of the blood withdrawal line or ofthe blood return line;

at least a post-infusion line connected to the blood return lineupstream of the heating zone;

an air trapping device placed on the blood return line upstream of theheating zone.

This configuration allows to prevent air intake at the blood warmerinlet. Since air intake is prevented, more design options may beconsidered for the warmer: freedom on warmer orientation (e.g. verticalbag) and freedom in warmer concept. Optionally, the blood treatmentdevice has a first compartment or blood chamber and a second compartmentor fluid chamber separated from one another by a semipermeable membrane;the blood withdrawal line is connected to an inlet port of the bloodchamber; the blood return line is connected to an outlet port of theblood chamber.

Optionally, the apparatus comprises a fluid evacuation line connectedwith an outlet port of the fluid chamber.

Optionally, the apparatus comprises a dialysis line connected to aninlet port of the fluid chamber.

In a 2^(nd) aspect according to the previous aspects, the post-infusionline is connected to the air trapping device.

In another aspect, the post-infusion line may be connected to the bloodreturn line upstream of the air trapping device.

In a 3^(rd) aspect according to the previous aspects, the extracorporealblood treatment apparatus comprises a secondary post-infusion line influid communication with the blood return line upstream of the heatingzone and connected to said blood return line downstream of the heatingzone, to bypass the blood warmer. The post-infusion circuit is split intwo streams: a main stream connected to the air trapping device and asecondary stream connecting the blood circuit downstream of the bloodwarmer. The main stream flows through a line segment of thepost-infusion line comprised between a branching off point and the airtrapping device. The secondary stream flows through the secondarypost-infusion line.

In a 4^(th) aspect according to the previous aspect, upstream of theheating zone, the secondary post-infusion line is connected to thepost-infusion line.

In a 5^(th) aspect according to aspects 3 or 4, the secondarypost-infusion line is connected to the post-infusion line upstream ofthe air trapping device.

In another aspect, the secondary post-infusion line is connected to theair trapping device.

In a 6^(th) aspect according to any of aspects 3 to 5, the apparatuscomprises control devices operatively active on the post-infusion lineand on the secondary post-infusion line, for controlling a flow throughsaid post-infusion line and through said secondary post-infusion line,optionally through the line segment of said post-infusion line andthrough said secondary post-infusion line.

In a 7^(th) aspect according to the previous aspect, the control devicescomprises a by-pass pump placed on the secondary post-infusion line,optionally said by-pass pump is a peristaltic pump, optionally saidby-pass pump is a finger pump, optionally said pump is a diaphragm pump.Use of a peristaltic pump on the secondary post-infusion line preventsblood from by-passing the blood warmer in case the post-infusion flow isstopped during treatment. The peristaltic pump allows for continuousflow in the secondary post-infusion line. The flow rate in this line maybe in the range of 50 ml/h to 6000 ml/h, optionally of 50 ml/h to 4000ml/h, optionally of 50 ml/h to 2000 ml/h. In case the set post-infusionflow rate is in the same order of magnitude, the pump may operate in aperiodic mode. Continuous or periodic flow in the secondarypost-infusion line prevents blood clotting at its connection with theblood circuit, as well as blood back-flow in the case a pressure pod isimplemented in this circuit section.

In a 8^(th) aspect according to aspect 6, the control devices comprisesa pinch valve placed between the post-infusion line and the secondarypost-infusion line at a branching off point of the secondarypost-infusion line.

In a 9^(th) aspect according to aspect 6, the control devices comprisesa flow resistor placed on the secondary post-infusion line.

In a 10^(th) aspect according to aspect 6, the control devices comprisesa secondary post-infusion clamp placed on the secondary post-infusionline.

In a 11^(th) aspect according to the previous aspect 9 or 10, thecontrol devices comprises a post-infusion clamp placed on thepost-infusion line downstream of the branching off point of thesecondary post-infusion line. The post-infusion clamp is placed on theline segment.

In a 12^(th) aspect according to the previous aspect 9 or 10, thecontrol devices comprises a non-return valve placed on the post-infusionline downstream of the branching off point of the secondarypost-infusion line. The non-return valve is placed on the line segment.

In a 13^(th) aspect according to the previous aspects, a return pressuresensor is placed on the blood return line downstream of the heatingzone.

In a 14^(th) aspect according to the previous aspects form 3 to 12, areturn pressure sensor is placed on the secondary post-infusion line.The presence of the return pressure sensor on the secondarypost-infusion line, instead of in the blood return line, allows tomonitor the return pressure as well as the blood warmer pressure dropand prevents additional clotting risks.

In a 15^(th) aspect according to the previous aspects, an auxiliary airtrapping device is placed downstream of the heating zone.

In a 16^(th) aspect according to the previous aspect, the auxiliary airtrapping device is identical to the air trapping device.

In a 17th aspect according to previous aspect 15 or 16, a returnpressure sensor is operatively active in the auxiliary air trappingdevice.

In a 18^(th) aspect according to previous three aspects when aspect 14refers to anyone of aspects from 3 to 12, the secondary post-infusionline is connected to the blood return line downstream of the heatingzone at the auxiliary air trapping device. Adding the auxiliary airtrapping device downstream the blood warmer is a better solution fromthe robustness and usability point of view, since any remaining airbubble at the end of the secondary post-infusion line is evacuated inthe auxiliary air trapping device.

In a 19^(th) aspect according to previous aspect 15, the auxiliary airtrapping device is a filled air trap.

In a 20^(th) aspect according to the previous aspect, the extracorporealblood treatment apparatus comprises an auxiliary blood line connecting atop of the filled air trap to the air trapping device.

In a 21^(st) aspect according to the previous aspect, an auxiliary bloodpump is placed on the auxiliary blood line and it is configured to pumpblood from the filled air trap back to air trapping device. Theauxiliary blood pump ensures a continuous flow from the blood filled airtrap to the air trapping device, in order to both remove air bubbles assoon as they are captured in the filled air trap, and to preventclotting in the auxiliary blood line between the two chambers. Thiscircuit design allows operating the blood warmer 15 in safe conditionswith respect to warming accuracy and clotting risk by preventing too lowflow rate and most flow stops inside the blood warmer 15, thanks to therecirculation loop. This recirculation capability in the blood warmer 15allows also for designing, if needed, degassing manoeuvres during thepriming sequence, with the possibility to create and alternate positiveand negative pressure in the warmer circuit section. In a 22^(nd) aspectaccording to the previous aspects, a warmer clamp is placed on the bloodreturn line between the air trapping device and the heating zone. Thesecondary post-infusion line and the warmer clamp make possible toby-pass the blood warmer during the early priming steps where anair-fluid mixture flows out from the blood treatment device, with aswitch back to normal flow in the blood warmer once most of air bubbleshave been removed and the air chamber of the air trapping device hasbecome fully effective in removing the remaining air bubbles.

Circuit variants with two chambers (air trapping device and auxiliaryair trapping device) may not require any warmer clamp in the bloodcircuit section including the blood warmer, provided that limitedamounts of air will remain in the device at the end of the primingsequence.

In a 23^(rd) aspect according to the previous aspects, an air bubbledetector is placed downstream of the heating zone. The downstreamposition of the air bubble detector has the benefit to prevent anytrouble in case of priming defects and subsequent release of air duringtherapy, like risk of patient air embolism or risk of air infusion topatient.

In a 24^(th) aspect according to the previous aspects, a pressuremonitor is operatively active in the air trapping device.

In a 25^(th) aspect according to the previous aspects, the apparatuscomprises a blood warmer operatively active on the heating zone, inparticular the blood return line being engaged with the blood warmer 20so that the blood warmer 20 is arranged to transfer heat to bloodflowing in the blood return line at the heating zone, for example theblood return line including a warmer bag at the heating zone. The warmerbag may comprise two films defining a blood path there-between from aninlet to an outlet for the blood.

In accordance with 26^(th) independent aspect, a method for priming anextracorporeal blood circuit of an extracorporeal blood treatmentapparatus, optionally through the apparatus according to anyone of theprevious aspects, before starting patient treatment, comprises:

filling the extracorporeal blood circuit of the extracorporeal bloodtreatment apparatus with a priming fluid and making the priming fluidflowing at least through a blood treatment device and through at least ablood return line towards a heating zone of said blood return line;

wherein, during an initial time interval, the priming fluid is divertedinto a secondary post-infusion line, in fluid communication with theblood return line upstream of the heating zone and connected to theblood return line downstream of the heating zone, to bypass a bloodwarmer operatively active on said heating zone;

wherein, after said initial time interval, the diversion is interruptedso that the priming fluid flows through an air trapping device placed onthe blood return line upstream of the heating zone and then through saidheating zone towards a terminal end of the blood return line.

In a 27^(th) aspect according to previous aspect 26, during the initialtime interval, the priming fluid flows through a post-infusion lineconnected to the blood return line upstream of the heating zone.

In a 28^(th) aspect according to previous aspect 26 or 27, after theinitial time interval, the priming fluid flows through a post-infusionline connected to the blood return line upstream of the heating zone.

In 29^(th) aspect according to previous aspect 26, 27 or 28, during theinitial time interval, the priming fluid flows through the air trappingdevice.

In 30^(th) aspect according to one of previous aspects from 26 to 29,during the initial time interval, the priming fluid flows from the bloodreturn line placed upstream of the heating zone, through the airtrapping device and then into the secondary post-infusion line.

In a 31^(st) aspect according to one of previous aspects from 26 to 29,after the initial time interval, the priming fluid flows from apost-infusion line connected to the blood return line upstream of theheating zone, through the air trapping device and then into the bloodreturn line downstream of the air trapping device.

In a 32^(nd) aspect according to one of previous aspects from 26 to 31,after said initial time interval, the priming fluid, flowing through apost-infusion line connected to the blood return line upstream of theheating zone, is split into the air trapping device and into thesecondary post-infusion line.

In a 33^(rd) aspect according to one of previous aspects from 26 to 32,during the initial time interval, a warmer clamp placed on the bloodreturn line between the air trapping device and the heating zone isclosed, thus allowing the priming fluid coming from the post-infusionline and the priming fluid coming from the blood return line and flowingthrough the air trapping device to flow through the secondarypost-infusion line.

In a 34^(th) aspect according to the previous aspect, after the initialtime interval, the warmer clamp is open, thus allowing the priming fluidcoming from the post-infusion line to flow through the secondarypost-infusion line and/or into the air trapping device and allowing thepriming fluid coming from the blood treatment device to flow through theair trapping device and through the heating zone.

In a 35^(th) aspect according to the previous aspects 33 or 34, duringthe initial time interval a pinch valve, placed between the mainpost-infusion line and the secondary post-infusion line at a branchingoff point of the secondary post-infusion line, is set in a neutralposition so that the air trapping device is in fluid communication withthe secondary post-infusion line.

In a 36^(th) aspect according to the previous aspects 33 or 34, duringthe initial time interval a post-infusion clamp, placed on thepost-infusion line downstream of the branching off point of thesecondary post-infusion line, is open so that the air trapping device isin fluid communication with the secondary post-infusion line.

DESCRIPTION OF THE DRAWINGS

The following drawings relating to aspects of the invention are providedby way of non-limiting example:

FIG. 1 shows a schematic representation of an extracorporeal bloodtreatment apparatus provided with an air trapping device and of a bloodwarmer according to the invention;

FIG. 2 shows another embodiment of the apparatus of FIG. 1;

FIG. 3 shows a portion of the apparatus of FIG. 1 in a first operativeconfiguration;

FIG. 4 shows the portion of FIG. 3 in a second operative configuration;

FIG. 5 shows a variant of the portion of FIG. 3 and FIG. 4;

FIG. 6 shows another variant of the portion of FIG. 3 and FIG. 4;

FIG. 7 shows another variant of the portion of FIG. 3 and FIG. 4;

FIG. 8 shows another variant of the portion of FIG. 3 and FIG. 4;

FIG. 9 shows another variant of the portion of FIG. 3 and FIG. 4;

FIG. 10 shows another embodiment of the portion of FIG. 3 and FIG. 4;

FIG. 11 is a flow chart of a priming procedure of the apparatus of FIG.3 according to a method of the invention.

DETAILED DESCRIPTION

With reference to the appended drawings, FIG. 1 shows a schematicrepresentation of an extracorporeal blood treatment apparatus 1.

The apparatus 1 comprises one blood treatment device 2, for example ahemofilter, a hemodiafilter, a plasmafilter, a dialysis filter, amembrane oxygenator, an adsorption device or other unit suitable forprocessing the blood taken from a patient P. The blood treatment device2 has a first compartment or blood chamber 3 and a second compartment orfluid chamber 4 separated from one another by a semipermeable membrane5. A blood withdrawal line 6 is connected to an inlet port 3 a of theblood chamber 3 and is configured, in an operative condition ofconnection to the patient P, to remove blood from a vascular accessdevice inserted, for example in a fistula on the patient P. A bloodreturn line 7 connected to an outlet port 3 b of the blood chamber 3 isconfigured to receive treated blood from the treatment unit 2 and toreturn the treated blood, e.g. to a further vascular access alsoconnected to the fistula of the patient P. Note that variousconfigurations for the vascular access device may be envisaged: forexample, typical access devices include a needle or catheter insertedinto a vascular access which may be a fistula, a graft or a central(e.g. jugular vein) or peripheral vein (femoral vein) and so on. Theblood withdrawal line 6 and the blood return line 7 are part of anextracorporeal blood circuit of the apparatus 1.

The extracorporeal blood circuit 6, 7 and the treatment unit 2 areusually disposable parts which are loaded onto a frame of a bloodtreatment machine, not shown.

As shown in FIG. 1, the apparatus 1 comprises at least a first actuator,in the present example a blood pump 8, which is part of said machine andoperates at the blood withdrawal line 6, to cause movement of the bloodremoved from the patient P from a first end of the withdrawal line 6connected to the patient P to the blood chamber 3. The blood pump 8 is,for example, a peristaltic pump, as shown in FIG. 1, which acts on arespective pump section 6 a of the withdrawal line 6. When rotated,e.g., clockwise, the blood pump 8 causes a flow of blood along the bloodwithdrawal line 6 towards the blood chamber 3 (see the arrows in FIG. 1indicative of the blood flow along the blood withdrawal line 6).

It should be noted that for the purposes of the present description andthe appended claims, the terms “upstream” and “downstream” may be usedwith reference to the relative positions taken by components belongingto or operating on the extracorporeal blood circuit. These terms are tobe understood with reference to a blood flow direction from the firstend of the blood withdrawal line 6 connected to the patient P towardsthe blood chamber 3 and then from the blood chamber 3 towards a secondend of the blood return line 7 connected to the vascular access of thepatient P.

The apparatus 1 further comprises an air trapping device 9 operating onthe blood return line 7 (the air trapping device 9 is a venousdeaeration chamber). The air trapping device 9 is placed online in theblood return line 7.

A first section of the blood return line 7 puts in fluid communicationthe outlet port 3 b of the blood chamber 3 with the air trap 9 and asecond section of the blood return line 7 puts in fluid communicationthe air trap 9 with the patient P.

The blood coming from the blood chamber 3 of the treatment device 2enters and exits the air trap 9 before reaching the patient P.

The apparatus 1 further comprises one fluid evacuation line 11 connectedwith an outlet port 4 b of the fluid chamber 4 such as to receive atleast a filtered fluid through the semipermeable membrane 5. Theevacuation line 11 receives the waste fluid coming from the fluidchamber 4 of the treatment device 2, for example, comprising useddialysis liquid and/or liquid ultra-filtered through the membrane 5. Theevacuation line 11 leads to a receiving element, not shown, for examplehaving a collection bag or a drainage pipe for the waste fluid. One ormore dialysate pumps, not shown, may operate on the evacuation line 11.

In the example of FIG. 1, a dialysis line 10 is also present, forsupplying a fresh treatment fluid to an inlet port 4 a of the fluidchamber 4. The presence of this dialysis line 10 is not strictlynecessary since, in the absence of the dialysis line, the apparatus 1 isstill able to perform treatments such as ultrafiltration, hemofiltrationor plasma-filtration. In case the dialysis line 10 is present, a fluidflow intercept device may be used, not shown, to selectively allow orinhibit fluid passage through the dialysis line 10, depending on whetheror not a purification by diffusive effect is to be performed inside thetreatment device 2.

The dialysis line 10, if present, is typically equipped with a dialysispump, not shown, and is able to receive a fresh fluid from a module, forexample a bag or on-line preparation section of dialysis fluid, and tosend such a fluid to the inlet port 4 a of the fluid chamber 4. Thefluid evacuation line 11, the dialysis line 10, and the fluid chamber 4are part of a treatment fluid circuit.

Finally, the apparatus 1 as shown comprises an infusion circuitcomprising one or more infusion lines 12, 13 of a replacement fluid: forexample a pre-infusion line 12 may be connected to the blood withdrawalline 6 and/or a post-infusion line 13 may be connected to the bloodreturn line 7. Infusion pump or pumps, not shown, equips typically theinfusion circuit. The pre- and/or post-infusion lines 12, 13 may besupplied by fluid coming from bags or directly by infusion fluidprepared on-line.

The post-infusion line 13 is connected to the blood return line 7through the air trapping device 9 to supply fluid to the blood at saidair trapping device 9. According to a different embodiment, not shown,the post-infusion line 13 is connected to the blood return line 7upstream the air trapping device 9.

Downstream of the air trapping device 9, the blood return line 7presents a heating zone 14 coupled or configured to be coupled to ablood warmer 15. It follows that the post-infusion line 13 is connectedto the blood return line 7 upstream of the heating zone 14 and that theair trapping device 9 is placed on the blood return line 7 upstream ofthe heating zone 14.

The blood warmer 15 is associated with the apparatus 1 to form anassembly which is structured to treat blood and keep blood withinpredetermined desired temperature boundaries. The blood warmer 15 may bean independent device (e.g. a stand alone unit physically separated fromthe apparatus 1) cooperating with the apparatus 1 and—inparticular—warming the heating zone 14. Alternatively, the blood warmer15 may be a component of the apparatus 1. In this case the blood warmer15 is not an independent stand alone unit, but rather part of theapparatus 1.

In both cases, the blood warmer 15 has a heating unit, not shown,configured for receiving and heating the heating zone of the bloodreturn line 7. For instance, the heating zone 14 of the blood returnline 7 may be in the form of a substantially flat bag insertable in aheating seat provided in the heating unit of the blood warmer. The flatbag presents an inlet and an outlet connected to the extracorporealblood circuit. Alternatively, the heating zone 14 may include a sectionof the tubing or a rigid cassette inserted into the heating unit of theblood warmer 15, which heating unit for instance may comprise a heatingsleeve or a heating coil wound around the heating zone 14. In practicethe heating unit has heating elements (e.g. electric impedances,infrared emitters or other types of heating elements) configured to heatthe corresponding heating zone 14 of the blood return line 7.

In the embodiment shown in FIG. 1, an air bubble detector 16 is placeddownstream of the heating zone 14, between a terminal end with accessdevice of the blood return line 7, connected to the patient P, and saidheating zone 14.

In order to make possible troubleshooting of air bubble detector 16alarms, the blood return line 7 may also include a puncture site, notshown, upstream the air bubble detector 16 and clamp for the air removalprocedure.

A return pressure sensor 17 is placed on the blood return line 7,between the heating zone 14 and the air bubble detector 16, to monitorpressure downstream of the blood warmer 15. Pressure upstream the bloodwarmer 15 may be monitored in the air trapping device 9 through apressure monitor 17′ which is operatively active in said air trappingdevice 9, by way of example through an air filled service line requiredfor a level adjustment in the air trapping device 9.

The apparatus shown in FIG. 1 further comprises a withdrawal clamp 18placed close to a terminal end of the blood withdrawal line 6 and areturn clamp 19 placed close to the terminal end of the blood returnline 7.

The air bubble detector 16 is connected to a control unit 100 of theapparatus 1 and sends to the control unit 100 signals for the controlunit 100 to cause closure of the return clamp 19 in case one or morebubbles above predetermined safety thresholds are detected.

The control unit 100, during treatment, may be configured to control theblood pump 8 based, by way of example, on a set blood flow rate. Thecontrol unit 100 of the apparatus 1 may also be configured to controlthe flow rate of dialysis fluid through the dialysis line 10, ofevacuation fluid through the evacuation line 11, of infusion fluid/sthrough pre-infusion line 12 and post-infusion line 13.

The control unit 100 of the apparatus 1 may also be configured tocontrol the blood warmer 15, during treatment, to keep blood within saiddesired temperature boundaries. The control unit 100 may comprise adigital processor (CPU) and memory (or memories), an analog circuit, ora combination thereof.

In use, during patient P treatment, the blood coming from theextracorporeal blood treatment device 2 and the infusion fluid flowingin the post-infusion line 13 enter the air trapping device 9 beforeflowing through the heating zone 14. This allows to prevent air intakeat the blood warmer 15 inlet.

In addition, the air trapping device 9 may have at least a low levelliquid sensor, not shown in figures, alerting the operator for adjustingthe chamber level of said air trapping device 9 before air bubbles aremoved to the blood warmer and to the air bubble detector 16.Alternatively, the circuit may include a second air bubble detector 16′(dashed line in FIG. 1) located immediately downstream of the airtrapping device 9. The apparatus 1 of FIG. 1 is fully robust to thepresence of some air bubbles in the post-infusion fluid.

With respect to the apparatus of FIG. 1, the apparatus 1 shown in FIG. 2further comprises a secondary post-infusion line 20. Said secondarypost-infusion line 20 is connected to the post-infusion line 13 at abranching off point 21 located upstream of the air trapping device 9.The post-infusion line 13 of the apparatus of FIG. 2 has a line segment13′ comprised between the branching off point 21 and the air trappingdevice 9. In another embodiment, not shown, the secondary post-infusionline 20 is connected to the air trapping device 9 (the branching offpoint 21 is located on the air trapping device 9). Said secondarypost-infusion line 20 is connected to the blood return line 7 at aconnection point 22 placed downstream of the heating zone 14 andupstream of the air bubble detector 16. In this way, the secondarypost-infusion line 20 by-passes the heating zone 14 and the blood warmer15.

A by-pass pump 23 is placed on the secondary post-infusion line 20. Thereturn pressure sensor 17 is placed on the secondary post-infusion line20 too (instead of on the blood return line 7 like in FIG. 1). A warmerclamp 24 is placed on the blood return line 7 between the air trappingdevice 9 and the heating zone 14. The by-pass pump 23 and the warmerclamp 24 are connected to the control unit 100, not shown in FIG. 2. Theby-pass pump 23 is a control device operatively active on the secondarypost-infusion line 20, for controlling a flow through said secondarypost-infusion line 20.

In use, during patient P treatment (FIG. 2) the warmer clamp 24 is open,the return clamp 19 is open and the heating zone 14 is placed in theblood warmer 15. The blood coming from the extracorporeal bloodtreatment device 2 and all or part of the infusion fluid flowing in thepost-infusion line 13 enter the air trapping device 9 before flowingthrough the heating zone 14. This allows to prevent air intake at theblood warmer 15 inlet. Through the by-pass pump 23, it is also possibleto control the post-infusion flow which is split between the airtrapping device and the return circuit downstream of the blood warmer15. The post-infusion flow rate may be in the range of 50 ml/h to 6000ml/h. The by-pass pump 23 may operate in continuous or in periodic mode.The blood warmer 15 may slightly overheat blood as to balance for thecooling effect of the secondary post-infusion, depending on the flowrates.

The presence of the secondary post-infusion line 20 during treatment mayrequire additional means in case the post-infusion contains some airbubbles. As infusion of such air bubbles downstream the blood warmer 15will create difficult troubleshooting situations, it may be of interestto prevent these events by: stopping temporarily flow in the secondarypost-infusion line 20 when presence of air bubbles is suspected (e.g.after a bag change); adding an air detector on the post-infusion 13upstream the post-infusion line split (an optical detection may besuitable for this purpose); having preventing means in the post-infusion13, such as a self-venting chamber using an hydrophobic membrane, andtaking advantage of the positive pressure present in the post-infusion13 upstream the air trapping device 9.

According to a method of the invention, the apparatus detailed above andshown in FIG. 2 allows to control the flow of a priming fluid throughthe heating zone 14, through the infusion line 13 and through thesecondary post-infusion line 20 when priming of the apparatus beforepatient P treatment is performed.

To this aim, the extracorporeal blood circuit of the extracorporealblood treatment apparatus 1 is loaded and filled with the priming fluidso that the priming fluid flows at least through the blood withdrawalline 6, through the blood treatment device 2 and through the bloodreturn line 7 towards the heating zone 14 of said blood return line 7.FIG. 11 shows a flow chart of one example of the priming procedure.

FIG. 3 shows the configuration of the apparatus 1 of FIG. 2 during aninitial time interval ΔT1 of the priming procedure. The initial timeinterval ΔT1 may last for about the time required to flow a primingfluid volume matching with the total blood circuit volume. Priming maybe done using the prescribed solutions for the patient treatment.

During said initial time interval ΔT1 the warmer clamp 24 is closed, thereturn clamp 19 is open. The by-pass pump 23 rotates clockwise to pumpfluid from the branching off point 21 towards the connection point 22 orthe by-pass pump 23 is not present and not active on the secondarypost-infusion line 20 (a pump segment of the secondary post-infusionline 20 is unloaded).

The priming fluid coming from the blood treatment device 2 and flowingthrough the section of the blood return line 7 placed upstream of thewarmer clamp 24 enters the air trapping device 9 but is prevented fromentering the heating zone 14.

Therefore, the priming fluid coming from the blood treatment device 2,once in the air trapping device 9, is compelled to flow into the linesegment 13′ of the post-infusion line 13 (comprised between the airtrapping device 9 and the branching off point 21) and then into thesecondary post-infusion line 20. Also the priming fluid coming from asource of priming fluid and flowing in a section of the post-infusionline 13 upstream of the branching off point 21 flows into the secondarypost-infusion line 20. All the priming fluid by-passes the heating zone14 and the blood warmer 15 and enters again the blood return line 7 atthe connection point 22.

Downstream of the connection point 22, the priming fluid flows towardsthe terminal end of the blood return line 7.

FIG. 4 shows the configuration of the apparatus 1 after the initial timeinterval ΔT1, during the remaining priming step. During said remainingpriming step, the warmer clamp 24 is open, the return clamp 19 is open,the pump segment of the secondary post-infusion line 20 is loaded ontothe by-pass pump 23 and the by-pass pump 23 rotates clockwise to pumpfluid from the branching off point 21 towards the connection point 22.The by-pass pump 23 is compatible with the priming by-pass phase withrelatively high flow rates and air-water mixture. Such a by-pass pump 23may be a peristaltic pump which pump segment is loaded after the by-passphase (initial time interval ΔT1). A diaphragm pump or a finger pump mayalso be considered.

The priming fluid coming from the blood treatment device 2 and flowingthrough the section of the blood return line 7 placed upstream of thewarmer clamp 24 enters and exits the air trapping device 9, flowsthrough a section of the blood return line 7 comprised between the airtrapping device 9 and the heating zone 14, then through said heatingzone 14 towards the connection point 22. The priming fluid coming fromthe source of priming fluid and flowing in a section of thepost-infusion line 13 upstream of the branching off point 21 is splitinto the line segment 13′ (and then into the air trapping device 9) andinto the secondary post-infusion line 20. Indeed, said priming fluidflows in part into the air trapping device 9 and then through theheating zone 14 and in part through the secondary post-infusion line 20towards the connection point 22. Downstream of the connection point 22,all the priming fluid flows towards the terminal end of the blood returnline 7.

FIG. 5 shows a variant of the apparatus of FIG. 2, in which the by-passpump 23 is not present and a 3-way pinch valve 25 is placed between thepost-infusion line 13 and the secondary post-infusion line 20 at thebranching off point 21. Said pinch valve 25 is a control deviceoperatively active on the post-infusion line 13 and on the secondarypost-infusion line 20, for controlling a flow through the line segment13′ of said post-infusion line 13 and through said secondarypost-infusion line 20.

In use, during patient P treatment the warmer clamp 24 is open. Thepinch valve 25 is periodically switched between a first and a secondposition. In the first position, the pinch valve 25 closes the secondarypost-infusion line 20 and let the infusion fluid to flow into the linesegment 13′ and into the air trapping device 9. In the second position,the pinch valve 25 closes the post-infusion line 13 and let the infusionfluid to flow through the secondary post-infusion line 20 and into theblood return line 7 downstream of the blood warmer 15. The pinch valvedesign shall be such that, when switching during patient P treatment, nodirect communication is present between the air trapping device 9 andthe blood return line 7 as to prevent blood flow by-pass through thesecondary post-infusion line 20.

When priming, during (warmer clamp 24 closed) and after (warmer clamp 24open) the initial time interval ΔT1, the pinch valve 25 is set in aneutral position so that the air trapping device 9 is in fluidcommunication with the secondary post-infusion line 20.

The variant of FIG. 6 differs from the apparatus of FIG. 5 in that thepinch valve 25 is substituted by a flow resistor 26 placed on thesecondary post-infusion line 20 in combination with a post-infusionclamp 27 placed on the line segment 13′ of the post-infusion line 13downstream of the branching off point 21. During treatment, thisprevents blood flow in the secondary post-infusion line 20 whenpost-infusion is stopped. The flow resistor 26 may be designed in orderto prevent blood flow by-pass in the secondary post-infusion line 20 assoon the post-infusion flow rate is large enough. The post-infusionclamp 27 on the line segment 13′ of the post-infusion line 13 isrequired for preventing blood flow by-pass when post-infusion isstopped.

The variant of FIG. 7 differs from the apparatus of FIG. 5 in that thepinch valve 25 is substituted by a secondary post-infusion clamp 28placed on the secondary post-infusion line 20 in combination with anon-return valve 29 placed on the line segment 13′ of the post-infusionline 13 downstream of the branching off point 21

The variant of FIG. 8 differs from the variant of FIG. 7 in that thesecondary post-infusion clamp 28 is substituted by a secondary flowresistor 30.

The embodiment of FIG. 9 differs from the apparatus of FIG. 5 in thatFIG. 9 further comprises another auxiliary air trapping device 31 and inthat no warmer clamp 24 is present. Said auxiliary air trapping device31 is placed on the blood return line 7 downstream of the heating zone14 and of the blood warmer 15. Downstream of the heating zone 14, thesecondary post-infusion line 20 is connected to the blood return line 7at the auxiliary air trapping device 31.

Moreover, the return pressure sensor 17 is not on the secondarypost-infusion clamp 28 but it is operatively active in the auxiliary airtrapping device 31. Optionally, fluid level is automatically monitoredin the chambers of both the air trapping devices 9, 31.

Other variants, not shown, of the embodiment of FIG. 9 (in which airtrapping devices 9, 31 are present both upstream and downstream of theblood warmer 15) may comprise the control devices (operatively active onthe post-infusion lines) shown in FIGS. 2-4 (post-infusion pump 23), 6(post-infusion clamp 27 and flow resistor 26), 7 (non-return valve 29and secondary post-infusion clamp 28), 8 (non-return valve 29 andsecondary flow resistor 30).

In other variants, not shown, of the embodiment of FIG. 9 (in which airtrapping devices 9, 31 are present both upstream and downstream of theblood warmer 15) no post infusion in the auxiliary air trapping device31 is present. In the case, like in the embodiment of FIG. 1, the bloodwarmer 15 has not to compensate for any post-infusion cooling effect.

Furthermore, the air trapping device 9 and the auxiliary air trappingdevice 31 may be each other identical, as in FIG. 9, or the auxiliaryair trapping device 31′ may be a filled air trap including a softdiaphragm for return pressure measurement.

FIG. 10 shows the filled air trap 31′ and an auxiliary blood line 32with an auxiliary blood pump 33 connecting the top of the filled airtrap 31′ to the air trapping device 9.

The auxiliary blood pump 33 may be a peristaltic pump. Pump flow ratemight be settled in a wide range from a few ml/min to 100 ml/min andmore. This auxiliary blood pump 33 does not need to be stopped in caseof alarm and system safe state with stop of the blood pump 8 and returnclamp 19 closure. The main purpose of this blood circuit loop is to flowair bubbles back to the air trapping device 9, which should provide formeans to remove this air.

In a variant of FIG. 10, not shown, the auxiliary blood pump 33 on theauxiliary blood line 32 is substituted by an additional clamp. Thisvariant plays with the position of two air trapping chamber for makingpossible the transfer of air bubbles from the filled air trap 31′ to theair trapping device 9, when stopping the blood flow and opening theadditional clamp.

In another variant of FIG. 10, not shown, the auxiliary blood line 32 isnot present.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andthe scope of the appended claims.

The invention claimed is:
 1. A method for priming an extracorporealblood circuit of an extracorporeal blood treatment apparatus, beforestarting patient treatment, the extracorporeal blood treatment apparatusincluding: (a) a blood treatment device; and (b) a blood warmer, and theextracorporeal blood circuit including: (i) a blood withdrawal line anda blood return line coupled to the blood treatment device, wherein theblood return line includes a heating zone coupled to the blood warmer;(ii) a blood pump configured to be coupled to a pump section either ofthe blood withdrawal line or of the blood return line; (iii) at least apost-infusion line connected to the blood return line upstream of theheating zone; and (iv) an air trapping device located along the bloodreturn line upstream of the heating zone, the method comprising: fillingthe extracorporeal blood circuit of the extracorporeal blood treatmentapparatus with a priming fluid, wherein the priming fluid flows at leastthrough the extracorporeal blood treatment device and through at leastthe blood return line towards the heating zone of said blood returnline; diverting, during an initial time interval, the priming fluid intoa secondary post-infusion line to bypass a blood warmer operativelyactive on said heating zone, wherein the secondary post-infusion line isin fluid communication with the blood return line upstream of theheating zone and is in fluid communication with the blood return linedownstream of the heating zone; and directing, after said initial timeinterval, the priming fluid to flow through an air trapping deviceplaced on the blood return line upstream of the heating zone and thenthrough said heating zone towards a terminal end of the blood returnline.
 2. The method of claim 1, wherein the extracorporeal bloodtreatment apparatus includes the secondary post-infusion line in fluidcommunication with the blood return line upstream of the heating zoneand in fluid communication with said blood return line downstream of theheating zone, to bypass the blood warmer.
 3. The method of claim 1,wherein during the initial time interval, the priming fluid flowsthrough the post-infusion line connected to the blood return lineupstream of the heating zone.
 4. The method of claim 1, wherein afterthe initial time interval, the priming fluid flows through thepost-infusion line in fluid communication with the blood return lineupstream of the heating zone.
 5. The method of claim 1, wherein duringthe initial time interval, the priming fluid flows through the airtrapping device.
 6. The method of claim 1, wherein during the initialtime interval, the priming fluid flows from the blood return line placedupstream of the heating zone, through the air trapping device and intothe secondary post-infusion line.
 7. The method of claim 1, whereinafter the initial time interval, the priming fluid flows from thepost-infusion line in fluid communication with the blood return lineupstream of the heating zone, through the air trapping device and intothe blood return line downstream of the air trapping device.
 8. Themethod of claim 1, wherein during the initial time interval, a warmerclamp placed on the blood return line between the air trapping deviceand the heating zone is closed, thus allowing the priming fluid flowingfrom the post-infusion line, and the priming fluid flowing from theblood return line and through the air trapping device, to flow throughthe secondary post-infusion line.
 9. The method of claim 1, whereinafter said initial time interval, the priming fluid, flowing through thepost-infusion line in fluid communication with the blood return lineupstream of the heating zone, is split into the air trapping device andinto the secondary post-infusion line.
 10. The method of claim 1,wherein after the initial time interval, the warmer clamp is opened,thus allowing the priming fluid flowing from the post-infusion line toflow through at least one of the secondary post-infusion line and theair trapping device, and allowing the priming fluid flowing from theblood treatment device to flow through the air trapping device andthrough the heating zone.
 11. The method of claim 1, wherein after theinitial time interval, the warmer clamp is opened, thus allowing thepriming fluid flowing from the post-infusion line to flow through atleast one of the secondary post-infusion line and the air trappingdevice, and allowing the priming fluid flowing from the blood treatmentdevice to flow through the air trapping device and through the heatingzone.
 12. The method of claim 1, wherein during the initial timeinterval a post-infusion clamp, placed on the post-infusion linedownstream of a branching off point of the secondary post-infusion line,is open so that the air trapping device is in fluid communication withthe secondary post-infusion line.